Add vega check for conventions a spec misses

Surfaces read a view that misses a convention as something else without
a word: a number label makes a list a table, a text tone disappears, a
list never shows its other columns, X_focus without a table becomes a
field, a second text input has nowhere to type. vega check MODULE names
each such place (the view or input and what the surface does instead)
and exits 1; the rules sit next to the code that reads the screen.

The checks build a spec that misses eight conventions and expect exactly
its nine findings, and none in the examples.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/vega.h b/src/vega.h
index 40aecaa..062639b 100644
--- a/src/vega.h
+++ b/src/vega.h
@@ -34,6 +34,11 @@ typedef struct {
 } VegaScreen;
 
 void vega_screen(VegaScreen *, const PureModule *);
+/* What a module seems to mean but does not meet: a list label that is not
+ * text, a _focus view without its table, a column a list never shows, a
+ * second text input. Each finding names the view or input it is about;
+ * returns how many there were. */
+unsigned vega_check(const PureModule *, void (*report)(void *, const char *name, const char *message), void *context);
 
 /* A view (row ignored) or a column at a row as text; numbers in Pure's
  * shortest form. false when it has no value (for example a missing item). */